The present invention relates to an imaging module that reads an image formed by a lens system by means of a solid-state imaging device of CCD (Charge Coupled Device) or the like.
Conventionally, there has been an imaging module that captures an image by means of a solid-state imaging device of CCD or the like as disclosed in JP 2001-313873 A (see FIGS. 2B and 3 thereof). In the imaging module, the solid-state imaging device is fixed to a frame that supports a lens system, with a cantilever structure via an intermediate retention member in order to facilitate positional adjustment of the solid-state imaging device with respect to the lens system.
Moreover, there is an imaging module, of which the schematic structure is shown in FIG. 4 (the imaging module is not a prior art and shown for the sake of convenience to clarify the problems of the present invention). The imaging module 1 is constructed of a lens assembly 2, a housing 3 that holds the lens assembly 2, and a board 5 to which an imaging device 4 is attached. As shown in FIG. 5, circuit devices 6 of DSP (Digital Signal Processor) and so on besides the imaging device 4 are mounted on the board 5, and the circuit devices 6 receive and process a signal from the imaging device 4 via wiring lines (not shown) on the board 5. The board 5 is made of a ceramic material of alumina or the like in order to improve heat radiation of the imaging device 4. Moreover, the housing 3 is made of a resin for achieving a light weight and a low cost.
The board 5 is adjusted in position with respect to the housing 3 so that the center position of the imaging device 4 coincides with an optical axis of the lens assembly 2 and fixed to the housing 3 by a fixation material 7 made of a ultraviolet curing type adhesive or the like.
Such imaging modules have been downsized and mounted on portable apparatuses of portable telephones and so on, and importance is attached to reliabilities of, in particular, impact resistance capabilities and temperature characteristics.
However, in the imaging module of JP 2001-313873 A, the imaging device is fixed to the frame by the intermediate retention member with the cantilever structure, and there is a difference in the thermal expansion coefficient between the imaging device and the intermediate retention member because of a material difference between the imaging device and the intermediate retention member. Accordingly, there is a problem that a deviation occurs between the optical axis of the lens system and the center of the imaging device when a temperature change occurs.
The imaging module 1 shown in FIG. 4 has a problem that the board 5 made of the ceramic material cracks at a portion indicated by arrow B when an impact is received in a direction of arrow A as a consequence of drop of the portable apparatus on a floor, a road surface or the like, resulting in a low impact resistance capability and malfunction of the imaging module 1.